Prevent IE9 Launching in Quirks Mode

Published:
April 8, 2017 Last Updated:
August 21, 2017

Whilst testing a website or web app using browserstack for example, you may get some unexpected behaviour with IE9 launching in quirks mode, this usually occurs when declaring the HTML5 document type: <!DOCTYPE html>

Quirks mode is used by some web browsers to maintain backwards compatibility with web pages, designed for legacy versions of Internet Explorer. To prevent this behaviour, place the following meta tag immediately after the head tag: